1. Field of the Invention
The present invention relates to a semiconductor memory device, and more particularly, to an electrically erasable programmable read only memory device, such as a flash memory device.
2. Description of the Related Art
Certain flash memory devices include a memory cell array composed of individual memory cells having floating gate transistors. The memory cell array typically includes a string arrangement of floating gate transistors, commonly referred to as a “NAND string” or “NAND unit”. Within a NAND string, the floating gate transistors are series connected between a ground select transistor and a string select transistor. A plurality of word lines are arranged in the flash memory device to cross the NAND string. Each one of the plurality of word lines is connected to a control gate corresponding to a floating gate transistor in NAND string. The NAND string is also connected to corresponding bit lines.
Exemplary memory cell arrays are disclosed, for example, in Korean Patent Document No. 0626394. Exemplary memory cell arrays are also disclosed, for example, in U.S. Pat. Nos. 6,751,124 and 6,807,098, the collective subject matter of which is hereby incorporated by reference.
A NAND string in a memory cell array may be divided into a plurality of sectors adapted to perform read/program operations in sector units. When a read/program operation is performed in relation to a selected sector, read/program operations in relation to non-selected sectors are inhibited. Although the memory cell array is divided into the plurality of sectors, string select transistors associated with multiple sectors may be commonly controlled by a single string selection line. Since string select transistors associated with multiple sectors are commonly connected by a single string selection line in the conventional architecture, a program disturb phenomenon may occur in memory cells associated with one or more unselected sectors during a program operation. Moreover, since string select transistors associated with multiple sectors are commonly connected to a single string selection line, electrical current may be unnecessarily consumed in one or more unselected sectors during a read operation.